JP2001242075A - Method and device for measuring light beam transmittance of applied matter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily and accurately measure reflectance of an object to be measured on a base body by a method and a device for measuring light beam transmittance of the object arranged on a proper base body. SOLUTION: By this method for measuring light beam transmittance, light beam transmittance of the object to be measured (cosmetics such as a sunscreen, for example) applied onto the base body (human skin, for instance) having a specific light reflectance is measured. In this method, a light beam having a plurality of continuous wavelengths including a predetermined wavelength is incident on the object to be measured on the base body from the measured object applied side, a reflectance primary differential value to the predetermined wavelength serving as a change rate of the reflectance to the predetermined wavelength is found, and on the basis of the reflectance primary differential value and the transmittance at the predetermined wavelength, transmittance of the object to be measured at the predetermined wavelength is found.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring the light transmittance of a coated object on an object to be measured provided on an appropriate substrate, and an apparatus for measuring the light transmittance of the coated object. In particular, the present invention relates to a method for measuring the light transmittance of a coated material and a device for measuring the light transmittance of a coated material, which are suitable for use when it is difficult to measure the transmittance of an object to be measured through the substrate, such as when the substrate is human skin.

[0002]

2. Description of the Related Art Sunlight falling on the earth from the sun has its components in the range from the ultraviolet region to the infrared region, and is light having characteristics that can be approximated as almost linear light. And recently, the human body of ultraviolet rays contained as components in this sunlight,
In particular, the effect on the skin is a problem.

[0003] Ultraviolet rays in sunlight reaching the ground surface have a wavelength of about 280 nm or more, and include as a component up to 400 nm which is a boundary with visible light. These ultraviolet rays cause erythema, blackening, wrinkles,
Since it has various effects such as the occurrence of skin cancer, it is desirable to provide appropriate protection so that ultraviolet rays do not reach the skin and the like. In order to meet such demands, it is necessary to develop cosmetics having a high shielding property against harmful ultraviolet rays and to accurately evaluate the ultraviolet shielding properties of the cosmetics.

However, when cosmetics such as creams and foundations for the purpose of protecting against ultraviolet rays are used on actual human skin, there is still no method for directly measuring the degree of ultraviolet shielding properties. There is no alternative but to conduct a test according to the SPF test method and confirm the presence or absence of erythema on the skin.

In the SPF test method, an object to be measured such as cosmetics is applied to human skin, irradiated with ultraviolet light, and expressed by the following formula.
In this method, the PF value is determined, and the magnitude of the PF value is used to evaluate the ultraviolet shielding effect of the object.

SPF = (Amount of ultraviolet light causing slight erythema on the portion to be measured) / (Amount of ultraviolet light causing slight erythema on the uncoated portion) However, the SPF measurement is time-consuming and requires human skin. Since it is difficult to frequently measure many objects to be measured, the method is not suitable for daily use in the field of cosmetics development. Therefore, several methods of evaluating the ultraviolet shielding effect capable of predicting the SPF to some extent have been proposed.

For example, a dilution transmittance method for dissolving or dispersing an object in a solvent and measuring transmittance and absorbance, a quartz plate thin film method for thinly coating the object on a quartz plate and performing spectral measurement, There is a translucent uneven plate coating method in which an object to be measured is applied to a semi-transparent plate having an uneven surface in consideration of surface irregularities, and spectral measurement is performed.

[0008] However, these alternatives are in v
The SPF value is calculated by a calculation formula from the amount of transmitted ultraviolet light measured in vitro, and each method is based on the assumption that a certain amount (usually 2 mg / cm ² ) is applied to human skin.

Therefore, it can be said that these alternative methods have a correlation with the SPF value based on the assumed application amount, but the application amount in actual use is unknown as described later, and therefore, It was not possible to accurately evaluate the ultraviolet shielding properties of the cosmetics applied to the cosmetics.

[0010]

In the following, it will be considered that the SPF value predicted by the alternative method or the SPF value measured by the specified application amount is insufficient in correlation with the actual ultraviolet shielding property.

The ultraviolet shielding property of an external cosmetic such as a cream or a foundation means the difficulty in transmitting ultraviolet light, that is, it largely depends on the transmittance of the external cosmetic.

[0012] Therefore, if the optical properties of the cosmetic are required, it depends only on the thickness (application amount) of the object to be measured. This optical property can be determined by using a spectrophotometer. Therefore, the details of the optical properties are not measured, but the above-mentioned translucent uneven plate coating method, which involves actually measuring the transmittance of the object to be measured, means that a measurement that is reasonable is performed. .

However, actual cosmetics (sunscreen)
The amount of application at the time of use usually fluctuates greatly depending on factors such as the type of the base of the cosmetic to be used, the usability, the appearance, and the preference of the user. Especially recently, high S
Due to the demand for cosmetics having a PF value, many cosmetics contain a large amount of ultraviolet light scattering agent. However, when these are applied thickly, the whiteness derived from the scattering material becomes conspicuous. It is anticipated that it will be used at the desired thickness, with restrictions on the agent.

Considering that the UV shielding property depends on the coating amount, it is expected from the UV shielding property obtained by the translucent uneven plate coating method on the assumption that a certain amount is applied in actual use. There is no guarantee that a good ultraviolet shielding property will be obtained. In other words, know the sunscreen's ultraviolet shielding effect when applying a certain amount, and, on average, when the sunscreen is used under various conditions, how much shielding effect it has and how much variation it has Knowing is also an important issue.

It has been reported that the sunscreen coating amount is in the range of 0.5 to 1.5 mg / cm ² . These results are quantified by component analysis after having the subject apply the sunscreen, wiping the sunscreen from the skin with absorbent cotton and physically separating the sunscreen. Alternatively, it is obtained by calculating the total application area on the body and calculating the average application amount from the total used amount. These methods are cumbersome and hard to say on a daily basis.

To add a further problem, the ultraviolet shielding property refers to the difficulty in transmitting ultraviolet light as described above. Even if the coating amount can be measured, it does not directly indicate the ultraviolet shielding property. Absent. The relationship between the coating amount and the ultraviolet transmittance has a deviation from the Lambert-Beer's law due to the influence of coating unevenness or the like. Therefore, it is necessary to measure the deviation width for each test sample.

[0017] From such a background, in addition to the conventional evaluation of the sunscreen property at the time of a certain amount of application, the sunscreen property at the time of actual use is evaluated for the sunscreen. The evaluation must take into account the effects of the environment and the environment in which it will be used, and that these evaluations must be performed easily and accurately.

Therefore, when a cosmetic product such as a sunscreen is applied to a substrate such as skin, it is possible to directly and simply evaluate how much ultraviolet shielding properties the product actually has on the substrate. Is an issue.

The transmittance T of an object to be measured on a substrate is determined.
In some cases, optical methods may be used.
To apply Kubelka-Munk's two-constant theory
Can be Specifically, the thickness of the DUT was made sufficiently thick
Reflectance R_∞Know the scattering coefficient and absorption coefficient
Of the substrate (K / S), the reflectance R of the substrate
_g, And the reflectance R of the object to be measured on the substrate
Derived from the following equations (4) and (5) described in
The transmittance T is calculated by the following equation (6), or R _∞Is small
In this case, equation (7), which is approximated to a simpler equation,
According to (8), the transmittance R of the measured object is measured.
Therefore, the previously measured R_∞And R_gCan be calculated from
It seems to be noh.

[0020]

(Equation 3) However, in the case of obtaining the ultraviolet transmittance of the sunscreen on human skin for the following reasons, the purpose cannot be achieved even by applying the equation (6) or the equation (7).

[0021] In R _∞ ultraviolet region of the sunscreen to be measured (280 ~ 400 nm), typically applied from often 0.1 or less, equation (7). When applying the sunscreen, the reflectivity of an ultraviolet reflectivity R _g human skin R
_∞ , but since the R _g of human skin is generally as small as 0.05 to 0.2, a very narrow dynamic range (R _g
It is necessary to measure in -R _∞) within.

[0022] Moreover, on the relationship between squaring and transmittance See equation (7), the reflectivity R or quickly relative decrease in transmittance approaching R _∞. Therefore, in the case of an object to be measured having a transmittance of 30% or less, it is necessary to measure the reflectance very accurately in order to calculate the transmittance accurately.

However, in general, in the measurement of reflectance of a living body such as human skin, the measured value is often not determined due to differences in skin flexibility and surface morphology. Further, the fluctuation of the calculated reflectance is too large to calculate the ultraviolet transmittance, and as a result, the formula shown by Kubelka cannot be used directly.

[0024] As a more fundamental problem, the surface reflected light intensity caused by difference in refractive index between the air is considered to differ in substrate surface and the workpiece surface, the reflectance was measured in equation (7) R _g and R There is a problem that _∞ cannot be substituted as it is. These are corrected by using surface reflection parameters based on the refractive index of the object to be measured as Saunderson's correction, but the surface reflection parameters of the object to be measured are unknown, and differences in surface shape and Since it is considered that the parameters fluctuate depending on the difference in the properties of the measuring instrument, it cannot be said that the correction can be performed accurately.

The present invention has been made in view of the above points, and a method of measuring a light transmittance of a coated material and a method of measuring a light transmittance of a coated material capable of easily and accurately measuring the transmittance of a measured object. It is intended to provide a device.

[0026]

Means for Solving the Problems In order to solve the above problems, the present invention is characterized by taking the following various means.

According to the first aspect of the present invention, there is provided a method for measuring the light transmittance of an object to be measured which is applied to a substrate having a specific light reflectance, the method comprising: Light of a plurality of continuous wavelengths, including the object to be measured, is incident on the object to be measured on the substrate from the side on which the object to be measured is applied, and the first derivative of the reflectance with respect to the predetermined wavelength, which is the rate of change of the reflectance with respect to the predetermined wavelength. And determining the transmittance of the measured object at the predetermined wavelength based on a relational expression between the reflectance first derivative and the transmittance at the predetermined wavelength.

According to a second aspect of the present invention, in the method for measuring the light transmittance of a coating material according to the first aspect, the first derivative of the reflectance with respect to the wavelength at the predetermined wavelength and the transmittance at the predetermined wavelength are determined. The relational expression is represented by the following expression (1).

[0029]

(Equation 4) The constant C in the above equation (1) is expressed by the following equation (2),
(3) simultaneous equations, the default value of maxR ', R _∞',
R _g ′,

[0030]

(Equation 5) And, wherein (1) R _∞ in equation ', R _g', C, and the R 'is a first-order derivative value reflectance at said predetermined wavelength of said object to be measured having an arbitrary thickness coated on the substrate By substituting, the transmittance T at the predetermined wavelength is obtained.

According to a third aspect of the present invention, there is provided a method for measuring the light transmittance of a coated article according to the first or second aspect,
The substrate is human skin.

According to a fourth aspect of the present invention, in the method for measuring the light transmittance of a coating material according to any one of the first to third aspects, the object to be measured is a cosmetic containing a sunscreen and a foundation. It is characterized by having.

According to a fifth aspect of the present invention, in the method for measuring the light transmittance of a coated article according to any one of the first to fourth aspects, the predetermined wavelength is in a range of 280 nm to 400 nm. Is what you do.

According to a sixth aspect of the present invention, there is provided an apparatus for measuring the light transmittance of a coating material, comprising: a light source for generating light having a plurality of continuous wavelengths including a predetermined wavelength; A light emitter that emits light to the device under test, a light receiver that collects reflected light from the device under test, and a light receiving element that photoelectrically converts the received light between the light source and the light projector or A spectroscope disposed on one of the light-receiving device and the reflected light data obtained by the light-receiving element, the reflectance at the predetermined wavelength, and the predetermined wavelength serving as a change rate of the reflectance with respect to the predetermined wavelength. And a calculating device for calculating the transmittance of the object at the predetermined wavelength based on the reflectance first derivative and the transmittance at the predetermined wavelength. Is what you do.

Each of the means described above operates as follows.

According to the first, second, and sixth aspects of the present invention, instead of directly treating the reflectance, the reflectance is converted into a first derivative of the reflectance with respect to a predetermined wavelength and used to obtain the surface reflected light. Such a component having no wavelength dependence can be canceled, and the correction process for the component having no wavelength dependence can be eliminated. Also, R _∞ ',
The relationship between the reflectance first derivative and the transmittance can be derived from R _g ′ and maxR ′, and the light transmittance of a coating material applied at an arbitrary thickness (amount) can be obtained from the reflectance first derivative. Can be.

According to the third aspect of the present invention, since the substrate is made of human skin, an object to be measured, such as a cosmetic, intended to be applied on human skin, is made of a material other than human skin. The light transmittance on the human skin can be measured without using a substitute (without using a substitute method).
Therefore, the light transmittance measurement on the object to be measured on human skin,
The measurement can be performed under conditions where the device under test is actually used, and the measurement accuracy can be improved.

According to the fourth aspect of the present invention, since the cosmetic containing sunscreen and foundation is used as the object to be measured, the actual ultraviolet light of the cosmetic containing sunscreen and foundation has an ultraviolet blocking effect. It is possible to obtain a blocking characteristic.

According to the fifth aspect of the present invention, by setting the predetermined wavelength in the range of 280 nm to 400 nm, it becomes possible to obtain a spectrum including ultraviolet rays which affect the skin. Acquisition of this spectrum makes it possible to evaluate the ultraviolet transmission characteristics of the object to be measured in more detail, and to clarify the properties of the object to be measured such as shielding against ultraviolet rays in more detail.

[0040]

Next, an embodiment of the present invention will be described.

The present inventor has conducted intensive studies on the above-mentioned problems of the conventional method for measuring the light transmittance, and as a result, it has been found that the reflectance for the wavelength to be measured (hereinafter, referred to as a predetermined wavelength) is not directly treated. Considering that the reflectance is converted into a first-order reflectance value for a predetermined wavelength and used. By performing such an operation, a component having no wavelength dependency such as reflected light is canceled, and therefore, there is an advantage that the above-described correction need not be particularly performed. Hereinafter, this point will be described using the following equations (9) to (11).

[0042]

(Equation 6) When the equation (7) described above is converted into a relational expression between the first-order reflectance value and the transmittance, the equation (9) is obtained. This equation (9)
In the above expression, (T ² ) ′ included in the right side is the above-described equation (8).
Is converted to the expression (10) using the relationship Then, by substituting equation (10) into equation (9), equation (1) is obtained.
Obtain 1).

The third term on the right side of the equation (11) includes an unknown parameter C _{1 and} also includes the reflectances R _g and R _で which are difficult to measure as described above. Therefore, the inventor further considered the equation (11).

Equation (11) shows the relationship between the first derivative of the reflectance and the transmittance. When the transmittance is 1, it is a first-order differential value of the reflectance when the object to be measured is not applied, that is, a first-order reflectance value R _g ′ of the substrate. When the transmittance is 0, the first derivative of the reflectance R _∞ ′ is obtained when the thickness of the object to be measured is infinitely increased and the transmittance can be regarded as substantially 0. Accordingly, when the thickness of the object to be measured is gradually increased from 0 and the transmittance of the object to be measured approaches 1 to 0, R
Draw the process of moving from _g 'to _R∞ '.

At this time, (R _g −
If R _∞) C ₁ is certain conditions are met, specifically, not 0, the reflectivity primary differential value R 'is believed to take an extreme value when there specific transmittance ((R _g −R _∞ ) C ₁
If <0, the maximum value. Hereinafter, assuming the maximum value, R ′ at that time is expressed as maxR ′). This max
It is not difficult to obtain R ′ experimentally, and it is possible to obtain R ′ from the behavior of the first derivative of the reflectance at that time by gradually coating the object to be measured on the substrate.
Next, try to determine the 'T _maxR when giving _the' maxR.
At this time, since dR ′ / dT = 0 is satisfied, the following equation is established in which the right side of equation (11) is differentiated by T and the left side is set to 0.

[0046]

(Equation 7)Equation (11) is used to calculate maxR ',
R_g’, And R_∞′, Equations (11) and (1)
From the simultaneous equations of 2), (R_g-R_∞) C₁And T
_{maxR '}Can be calculated. As a result, the expression
The relationship between the first derivative of the reflectance and the transmittance of (11) is determined.
You. That is, the point of the present invention is that the maxR 'that can be measured is
By using the relationship of equation (12), the first derivative of the reflectance
This is to derive a relational expression between the value and the transmittance.

By using this relational expression, the transmittance can be calculated from the first derivative of the reflectance of the object to be measured applied in an arbitrary amount. Moreover, in a series of operations for obtaining the transmittance, only the first derivative of the reflectance is used as the measured value, and the reflectance data is not directly involved. Therefore, a component having no wavelength dependency such as surface reflected light can be canceled, and a correction process for the component having no wavelength dependency can be eliminated. This makes it possible to easily and accurately measure the reflectance of the device under test.

Next, a specific method for measuring the light transmittance based on the above principle will be described.

First, an apparatus for measuring light transmittance used in the method for measuring light transmittance will be described with reference to FIG. As shown in the figure, the measuring device 10 is a human skin 20 (substrate).
To be measured 21 (foundation,
It measures the light transmittance of cosmetics such as creams and sunscreens.
2, a light projector 13, a light receiver 15, a light receiving element 16, an arithmetic unit 17, and the like.

The light source 11 is intended to generate a light (Fukuiroko) for irradiating the object to be measured, Xe lamp, _{D 2} lamp,
W lamps are preferred. Further, the spectroscope 12 has a function of dispersing the light generated by the light source 11 and emitting only a predetermined range of wavelengths toward the light projector 13. Spectrometer 1
Reference numeral 2 denotes a configuration in which light in the wavelength range of 280 nm to 400 nm, that is, light having a wavelength in the ultraviolet region, is emitted toward the projector 13 in this embodiment. As long as the spectroscope 12 has a spectroscopic function, in addition to the diffraction grating, a prism,
A filter or the like is used. The wavelength resolution is sufficient if the half width is 20 nm or less.

The light projector 13 projects the light separated by the spectroscope 12 toward the device under test 21.
(Human skin 20). The light receiver 15 is also mounted on the device under test 21 (human skin 20), and is configured to be able to receive only diffusely reflected light excluding specular reflection from among the light reflected from the device under test 21. . An integrating sphere 14 for focusing the reflected light is provided between the light projector 13 and the light receiver 15.

The light receiver 15 is connected to the light receiving element 16. The light receiving element 16 photoelectrically converts the diffuse reflected light received by the light receiver 15 and generates reflected light data corresponding to the light intensity of the reflected light. The reflected light data generated by the light receiving element 16 is sent to the arithmetic unit 17. The arithmetic unit 17 obtains the first derivative of the reflectance from the reflected light data, and calculates the transmittance from the first derivative of the reflectance.

At this time, preferably, as shown in the figure, when the integrating sphere 14 is brought into close contact with the object 21 to be measured, the projector 13 is installed so as to irradiate the human skin 20 with light vertically.
The light receiver 15 is desirably installed so as to receive a light amount proportional to the intensity of diffusely reflected light from the device under test 21. Considering the convenience of the measurement, the integrating sphere 14 equipped with the projector 13 and the light receiver 15 is connected to the spectroscope 12 and the light receiving element 16 by a flexible material such as glass fiber or electric wire so as to be freely movable. It is desirable to do.

Further, the standard body is irradiated with light at the same time, and the reflected light intensity and the light intensity from the DUT 21 are simultaneously measured, or the light intensity applied to the DUT 21 is simultaneously monitored. Thus, a device for increasing the measurement accuracy may be added. Further, an optical method may be used such that two monochromatic lights having slightly different wavelengths are alternately irradiated on the DUT 21 and the first derivative of the reflectance is obtained from the difference between the light intensities.

Further, the spectroscope 12 includes a light source 11 and a light projector 13.
1 (the configuration shown in FIG. 1),
It may be set to any one of between and the light receiving element 16.
A monochromator can be placed between the light source 11 and the projector 13, and a photomultiplier tube can be used for the light receiving element 16. When the light receiving element 16 is placed between the light receiving element 15 and the light receiving element 16, a multi-channel detector can be used for the light receiving element 16 using a polychromator.

Next, the procedure for measuring the transmittance, which is performed using the measuring apparatus 10 having the above configuration, will be described.

First, the human skin 20 is irradiated with light of each wavelength in a continuous predetermined range including a predetermined wavelength (a target wavelength to be measured) and its reflectance is measured, and the reflectance first derivative R with respect to the predetermined wavelength is measured. _g ′.

Subsequently, a cosmetic to be measured 21 is applied on human skin 20. At this time, the transmittance of the measured object 21 at a predetermined wavelength is in the range of 60 to 80% by changing the applied amount thickness of the measured object 21 or by diluting and applying the measured object 21. To enter. Then, the object 21 is irradiated with light of each wavelength in a continuous predetermined range including the predetermined wavelength, the reflectance is measured, and the first derivative of the reflectance with respect to the wavelength at the wavelength is obtained. Furthermore,
The reflectance first derivative is similarly obtained by changing the coating thickness and the dilution ratio, and the maximum value maxR 'of the reflectance first derivative is obtained by repeating this operation.

Next, the object to be measured 21 is applied sufficiently thick, specifically, applied to the human skin 20 at a thickness at which the transmittance at the predetermined wavelength can be regarded as almost 0, and the reflectance at the predetermined wavelength is measured. , The first derivative of the reflectance R for this predetermined wavelength
_{Ask for ∞} '.

As described above, at the predetermined wavelength of the human skin 20
Reflectance first derivative R_g’, Maximum value of the first derivative of reflectance
maxR ', first derivative of reflectivity when applied sufficiently thick
R_∞′ Are obtained, each value R_g’, MaxR’, R
_∞Is substituted into the above equation (119, (12)).
Then, by serializing each equation, (R_g
-R_∞) C₁Can be requested. Incidentally, the expression of claim 2
In (1), (R _g-R_∞) C₁As a constant C
I have.

Subsequently, the reflectance primary differential value R ′ at a predetermined wavelength when the object 21 is arbitrarily applied to the human skin 20.
Is measured. Then, in the relational expression of the above-mentioned expression (11),
Previously obtained _{R ∞ ', R g',} (R g -R ∞) by substituting the _{C 1} and R ', transmittance at a predetermined wavelength T
Can be requested.

FIGS. 2 to 4 show the results of verification of the method for measuring the light transmittance according to the present invention. In this verification, a translucent uneven plate whose transmittance can be actually measured was used, and the transmittance obtained from only the first derivative of the reflectance was compared with the transmittance obtained by actual measurement. The result is shown in FIG. The figure shows that the measured transmittance is in good agreement with the logical curve obtained by the measuring method according to the present invention, and thus it has been proved that the measuring method according to the present invention is effective.

Next, the maximum value maxR 'of the first derivative of the reflectance when human skin is used as the substrate and the sunscreen is used as the object to be measured, and the relationship between the first derivative of the reflectance and the transmittance is determined. I asked. Fig. 3 shows the result as a graph.
Shown in

Next, when the same type of sunscreen as described above was applied to human skin at 0.5 to 2.0 mg / cm ² , the result of the transmittance calculated from the first derivative of the reflectance and the same amount of sunscreen were translucent. The measured transmittance (in vitr
FIG. 4 shows the transmittance determined by o. As is apparent from the figure, the two are almost the same, which demonstrates that the measurement method according to the present invention is also effective.

Note that the present measurement method started from an equation in which R _近似 is approximated in a relatively small wavelength region, but (R _g −R _∞ )
There is no particular limitation on the wavelength as long as C ₁ ≠ 0. Although not described in detail, although it is complicated from Equation (4), the unknown parameter can be similarly obtained using the first-order reflectance value.

However, the larger the difference between the extremum and R _∞ ′, that is, the larger | C ₁ | >> 0, the wider the dynamic range of the measurement and the higher the accuracy, and the smaller the R _∞ It is more practical to select such a wavelength especially and use it for the evaluation of ultraviolet shielding of a sunscreen or the like, for the reason that it is easy to perform. Specifically, in the case of a sunscreen, the present measurement method is effective particularly in a wavelength region where the transmittance changes largely around 350 to 380 nm.

[0067]

According to the present invention as described above, the following various effects can be realized.

According to the first, second, and sixth aspects of the present invention, instead of directly treating the reflectance, the reflectance is converted into a first derivative of the reflectance with respect to a predetermined wavelength to be used. Such a component having no wavelength dependence can be canceled, and the correction process for the component having no wavelength dependence can be eliminated. Also, R _∞ ',
The relationship between the first derivative of the reflectance and the transmittance can be derived from R _g 'and maxR', and the light transmittance of a coating material applied at an arbitrary thickness (amount) is obtained from the first derivative of the reflectance. Can be.

Further, according to the third aspect of the present invention, an object to be measured such as a cosmetic intended to be applied on human skin can be used without using an alternative other than human skin (using an alternative method). ), The light transmittance on the human skin can be measured. Therefore, the light transmittance measurement on the object to be measured on human skin can be performed under conditions where the object to be measured is actually used, and the measurement accuracy can be improved.

According to the fourth aspect of the present invention, it is possible to obtain the actual ultraviolet shielding properties of a cosmetic including a sunscreen and a foundation having an ultraviolet shielding effect.

According to the fifth aspect of the present invention, it is possible to obtain a spectrum including ultraviolet rays which affect the skin, and to obtain the spectrum to evaluate the ultraviolet transmission characteristics of the object to be measured in more detail. It becomes possible to clarify in more detail the properties of the object to be measured such as shielding against ultraviolet rays.

[Brief description of the drawings]

FIG. 1 is a diagram showing a main configuration of a light transmittance measuring apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram for demonstrating the usefulness of the method for measuring light transmittance according to the present invention (part 1).

FIG. 3 is a diagram for demonstrating the usefulness of the method for measuring light transmittance according to the present invention (part 2).

FIG. 4 is a diagram for demonstrating the usefulness of the method for measuring light transmittance according to the present invention (part 3).

[Explanation of symbols]

 Reference Signs List 10 light transmittance measuring device 11 light source 12 spectroscope 13 light emitting device 14 integrating sphere 15 light receiving device 16 light receiving element 17 arithmetic device 20 human skin 21 object to be measured

Claims (6)

[Claims] 1. A method for measuring the light transmittance of an object to be measured which is applied to a substrate having an inherent light reflectance, comprising: measuring a plurality of continuous wavelengths including a predetermined wavelength. Having the light incident on the object to be measured on the substrate from the side on which the object to be measured is applied, and obtaining a first derivative of the reflectance with respect to the predetermined wavelength, which is a change rate of the reflectance with respect to the predetermined wavelength, A method for measuring the light transmittance of a coating material, wherein the transmittance of the measurement object at the predetermined wavelength is obtained based on a relational expression between the first derivative of the rate and the transmittance at the predetermined wavelength. 2. The method for measuring the light transmittance of a coating material according to claim 1, wherein a relational expression between a first derivative of reflectance at a wavelength at the predetermined wavelength and a transmittance at the predetermined wavelength is represented by the following equation (1). ), And The constant C in the above equation (1) is expressed by the following equation (2),
(3) simultaneous equations, the default value of maxR ', R _∞',
R _g 'is obtained by substituting And, wherein (1) R _∞ in equation ', R _g', C, and the R 'is a first-order derivative value reflectance at said predetermined wavelength of said object to be measured having an arbitrary thickness coated on the substrate A method of measuring the light transmittance of a coating material, wherein the transmittance T at the predetermined wavelength is determined by substituting the values. 3. The method for measuring the light transmittance of a coated material according to claim 1 or 2, wherein the substrate is human skin. 4. The method according to claim 1, wherein the object to be measured is a cosmetic containing a sunscreen and a foundation. The method for measuring the light transmittance. 5. The method for measuring the light transmittance of a coated material according to claim 1, wherein the predetermined wavelength is in a range of 280 nm to 400 nm. Measuring method. 6. A light source for generating light of a plurality of continuous wavelengths including a predetermined wavelength, a projector for emitting light generated by the light source to an object to be measured, and condensing light reflected from the object to be measured. A light receiver, a spectroscope disposed between the light source and the light projector, or between the light receiver and the light receiver for photoelectrically converting the received light, and the light receiver. From the reflected light data, the reflectance at the predetermined wavelength and the first derivative of the reflectance for the predetermined wavelength, which is the rate of change of the reflectance for the predetermined wavelength, are calculated, and the first derivative of the reflectance and the transmittance at the predetermined wavelength are calculated. A calculating device for calculating the transmittance of the measured object at the predetermined wavelength based on the relational expression: